I took a short piece of footage into AE (1080p 23.98), put a 3D Camera Tracking effect on it (which seemed to work perfectly) then exported the Comp using MAXON CINEMA 4D EXPORTER and opened it with Cinema 4D. So far, everything working great.

Then I exported the original footage as a JPEG sequence to apply to Background Material to use as a reference in C4D. I added just one 3D element, extruded text, and playback looks great, everything's working as it should.

HOWEVER, if I render out the sequence with physical motion blur (only the extruded text--background not rendered), I get a couple instances in which it looks like the camera shifts and spins wildly for one or two frames, causing a twisting motion blur smear. It's almost like the camera is in the right spot in every frame, but somehow the renderer thinks that the camera is making wild moves IN BETWEEN the frames. Does that make sense? Rendering without motion blur works fine.

I tried it with different objects, and the smear is always at the same time and in the same direction, meaning it must be some miscommunication between the camera and the renderer. Perhaps it has something to do with framerate? C4D doesn't seem to do 23.98, so I'm just putting all settings to 24 across the board. Also, can't seem to find anyone else with this same problem.

I know I can force motion blur after render, but I don't want to just give up on physical motion blur because of these one or two weird frames. Any help?

Watching the coordinates of the 3D Tracker Camera in C4D, I've discovered that the H rotation coordinate jumps from .0007 degrees one frame, then to 359.845 degrees one frame later--a change that looks seamless to the eye, but in essence is whipping the camera around 360 degrees in one frame, an issue revealed only by adding motion blur. Now I think this post should be posted in the After Effects forum, because that's clearly where the problem lies.

Has anyone else had this problem with AE's 3D Camera Tracking exporting unreliable or non-adjacent coordinate data, and if so, is there a fix?